The present invention relates generally to a filtration membrane test unit or cell, and more particularly, to a cross-flow filtration membrane test unit or cell which more closely simulates the flow dynamics within a full-size filter unit, thereby providing better prediction of membrane filter performance.
Much of filtration technology today involves, among others, ultrafiltration (UF) and microfiltration (MF), which utilizes filtration membranes to separate particles of a desired size from a liquid. In the normal operational environment, a liquid containing the particles to be filtered is pressurized via a pump or other means and exposed to one side of the filtration membrane. The liquid is allowed to flow across such membrane before exiting through a concentration port. Because of the high pressures involved, a portion of the liquid is forced through the membrane with the remainder of the liquid and all particles over a given particle size being rejected and removed from the system through the concentrate outlet.
Because of the vast number of different liquids, slurries, etc. that can be subject to filtration utilizing this technology, there are a large number of possible membrane materials that can also be used. In selecting the proper membrane material, consideration must be given to, among many others, its compatability with the liquid being filtered, the size of particle desired to be rejected by the membrane and the pore size of the membrane. The testing of the filtration performance and characteristics of a particular membrane can be quite time consuming and costly if one has to construct a full size system in order to properly test the membrane. As a result, several products in the form of membrane test devices have been developed for the purpose of trying to predict the filter and flow characteristics of the membrane under normal operating conditions.
Some of the most common membrane test devices currently being used include devices which utilize membrane cassettes. Typical membrane cassette test units include the Pellicon and Minitan test units manufactured by Millipore, the Sartocon I and II test units manufactured by Sartorius and the Novosette test unit manufactured by Filtron. These systems can best be described as including two pieces of membrane adhesively bonded or heat sealed to a piece of plastic. The principal limitations of the membrane cassette systems are that they are, of course, limited to the membranes within the cassette, they are quite expensive, and they fail to closely simulate the actual flow dynamics of the full scale device.
Another prior art membrane test device includes the Megaflow TM-100 manufactured by New Brunswick. This device uses a single piece of membrane and is a cross-flow filtration device which utilizes channels machined into the apparatus to direct the feed flow. Because of this, its ability to simulate the flow dynamics of the full-size filtration unit is limited.
Further, the mechanism in these prior test units for creating the seal around the membrane has been less than desirable and often results in an inadequate seal and therefore leakage. The prior systems also require significant time to change from one membrane to another.
Accordingly, there is a need in the art for a filtration membrane test unit which is inexpensive to operate, which requires less time to change over from one membrane to the next, which provides an improved seal and which more closely simulates the flow dynamics of the full-size system.